How to Fix Sony KLV-40W652D Not Turning On

How to Fix Sony KLV-40W652D Not Turning On – Fault Traced to 39K Resistor on Main Board

A Sony LED TV, model number KLV-40W652D, was brought to my workshop for repair. The customer said that this TV sometimes turns on and mostly remains off. I switched on the TV for a quick inspection. In this model, the power supply is in the form of a separate adapter. I checked the DC output of this adapter, 19V, and it was there, so according to my estimation, there may be a fault in its main board. I told the customer that you should leave this TV with me. I will diagnose its fault and tell you the total cost. With your permission, I have published some articles on the same model in Different Findings. If you want, you can also read them on the same website. I will put a link in it. Technician friends can also benefit from them. The rest of us will explain the condition of this set step by step. Will do and try to make this a technician-friendly article.

Physical inspection 

First of all, I took this Sony LED TV to my workshop lab and opened it. The first thing I noticed was that there was a lot of dust in it. Dust is very annoying for such boards. I cleaned it. The main board was cleaned to a large extent, but it was still in very bad condition. Now I started inspecting it. First of all, I looked carefully at all the resistors to see if there were any burnt resistors. Then I looked carefully at all the capacitors because ceramic capacitors are used in it. Sometimes these capacitors also get shorted. And the short-circuiting, which is a type of short-circuiting, is also visible. However, I did not see anything like that in it. Then I looked at its main IC and examined it carefully. It was fine. I did not see any problem in it. Visually, it was fine. After that, I checked all the regulators of its buck converter.

Voltage Testing of KLV-40W652D

After that I started checking its main voltage 19 volt input supply which was coming, there was a five volt power supply, there are two more regulators in it which generate 3.3 volts, there were 3.3 volts output on them, 1.2 voltage and 1.5 voltage for the system IC and NAND flash IC, they were also coming, 1.8 voltage is in it to drive the tuner and they were also there, I checked they were also coming, the regulator that converts 19 volts to 12 volts which provides VCC supply to the panel was off, that is, it was not generating voltage, so this was its voltage testing, now this testing proves that its main system IC is not resetting, due to its not being reset, the red light is not turning on, now we will find out what is the reason for this, we will see in fault finding why our system is not resetting

39K Resistor Fault in System Reset Circuit

Now I have started checking its ceramic capacitors step by step. I checked almost all the capacitors. They were fine. Then I checked the crystal with the system. I checked that its connections are going properly. The system IC has a register in its series. It is fine. Yes, this register was giving me the correct value. After that, I checked all the resistances that connect the system and the NAND flash. These registers are of 75 ohms. Some of them are of 47 ohms. All these resistances were perfectly fine. There is a six-pin SMD next to the system IC. It has two transistors right next to it. This is a complete circuit that resets the system IC. Inside this circuit, I checked the resistors. Here, I found a resistor with a value of 39K. After changing this resistor, my board started working perfectly.

• 🔧 Fault Diagnosis
• ✅ All ceramic capacitors were tested and found OK.
• ✅ Crystal oscillator and its connections to the system IC were verified.
• ✅ Series resistor with the system IC showed correct value.
• ✅ All resistors connecting the system IC and NAND flash (75Ω & 47Ω) were in good condition.
• ✅ The reset circuit of the system IC was inspected thoroughly.
• ✅ A faulty 39K resistor was found near the reset transistors.
• ✅ Replacing the 39K resistor resolved the no-power issue.

Conclusion

This is a common Sony fault in this model. The most important thing to focus on in fault finding is the register. You have seen how we removed this fault, and that too by changing a register. There are many other factors that cause such faults. But in this case, we found out that the 39k register was faulty, and by changing it, we fixed the set. So, we should focus on the work and diagnose the fault correctly. We should go step by step. People who go step by step also diagnose the fault and do their work well. This is a sequence. To reach the fault, you should know that those who are new technicians and new learners should follow this pattern and do good fault finding. The purpose of sharing my article is also that people do their work well and earn their livelihood. So, this is good for me and good for you too. In this case, we saw that a 39K register was faulty, so we replaced it, and our board was fixed.

• Q1: Why does this model of Sony LED TV have a dead fault?
• A1: For example, take the case where we replaced the faulty register inside the reset circuit and our TV was fixed. The reason was that the 39K register was faulty.
• A: Otherwise, any voltage regulator may be damaged or not performing properly, meaning that the voltage may go up and down. This specific regulator may also be the reason.
• A: The most common cause of dead faults in this model is the 1.2 voltage regulator and the 1.5 voltage regulator. This is what I have generally seen.

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